This is the scene at Kryvyi Rih on Thursday, slightly reminiscent of the iconic burning oil wells of Operation Desert Storm. In fact the fate of these tanks may well be close to that of the Iraqi oil well. While human error is the most popular theory so far, the thought of sabotage does come to mind. Additionally, Interfax reports that the incident is currently being treated as criminal.

The tanks in question are two T-64s, a tank much ahead of its time back when it was first being fielded and still a relevant piece of equipment. The two T-64s come from the 17th armored brigade, the closest armored brigade to Donetsk Oblast. If this was indeed sabotage performed by an outside party it is unlikely to have been carried out by professional saboteurs, while the T-64 is still an apt tank it is among the older and more outdated tanks in the Ukrainian arsenal and the Russians should be far more concerned with the few T-84 Oplots Ukraine has.
With this in mind, the idea of a scared tank operator or an amateur pro-Russian rank within the most likely scenarios for what really happened to these two tanks.

The video above shows the tanks in the distance, you can hear the ammunition going off every now and then.